THE OSMOTIC CONCENTRATION OF THE SAP OF THE LEAVES OF MANGROVE TREES

Abstract

The morasses of insular and continental coasts in the tropical zone of both eastern and western hemispheres are largely occupied by a vegetation consisting almost exclusively of a number of species of trees or shrubs collectively designated as mangroves. These species, belonging to different genera and families, are characterized by striking morphological and biological features, for example, the prop or stilt roots of Rhizophora, the negatively geotropic roots, breathing roots or pneumatophores of Avicennia, and the remarkable vivipary and seedling dispersal of Rhizophora. These various peculiarities have attracted the universal interest of biological travelers in the tropics. The physiology of a group of organisms characterized by such morphological features and growing under environmental conditions so specialized presents a most interesting group of problems. When, however, one turns to the literature he is impressed by the fact that conclusions concerning the physiology of these plants are chiefly deductions from all too superficial field observations and from macroscopic and microscopic anatomical investigations. Physiological constants, properly so called, are practically wanting. Thus the recording of any quantitative data on the physiology of this ecologically fascinating group of plants is especially desirable. In the present paper we shall not summarize or comment upon the available literature, but shall limit ourselves to the presentation of the results of certain measurements carried out on the southern shore of the island of Jamaica